As a game designer and frequent game player: Knowing that there are more abilities available in the future, but not what they are, is much, much worse than knowing the specific skill tree in advance. For the same reason, I'll take world one every time.

This can be explained by your own framework pretty easily, actually. In either case, you know that there are shiny new abilities you will gain later. If they are known, you may regret and/or resent not yet having them. How much worse, then, is it to know that they exist, but to have only your imagination to define them. Think about a young teenager who imagines how great it must be to be able to drive yourself around, compared to the reality of running errands and traffic. If you know what options you missed, there will be specific things you regret not having, but if all you know is that you missed some options, you can (and will) regret not having everything, even things it was never possible for you to get.

Also, if you know the fabulous capabilities you can achieve with time and effort along a path, that's a powerful motivating force, and moreso when you can see the clear steps along the path than when it's hidden and of unknown length.